This invention relates to a method of measuring minute three-dimensional structure on surfaces of materials with a Scanning Electron Microscope (referred to as "SEM" hereinafter) and more specifically to a method of measuring the depth of holes or grooves on surfaces of semiconductors and the magnitude of side-etching non-destructively with SEM.
An example of existing semiconductor surface inspection methods include that by, P. H. Singer which has been described in Semiconductor International Vol. 16, No. 3, pp. 48-54 (1983) under the title of "Linewidth Measurement: Approaching the Submicron Dimension". As shown therein, highly accurate linewidth measurement is possible with SEM. SEM have very large focus depth and by stereo measurement, measurement in the height direction is also possible and has been attracting public attention in relation to the measurement of sectional structures on surfaces of Very Large Scale Integrated Circuits (referred to as "VLSI" hereinafter). In addition to simple stereo methods, methods making use of knowledge on the structure of the area of interest have been also conceived. S. J. Finnes and G. J. Smith have described such a method in IBM Technical Disclosure Bulletin Vol. 26, No. 1 (1983), pp. 189-190, under the title of "Nondestructive Slope/Thickness Measurement for Semiconductor Topology". However, such a method cannot be used when holes or grooves are deep and the bottom area cannot be seen clearly. Also, some sample stands of VLSI length measuring SEM have no inclining function and the above method can not be used in such cases. On the other hand, measurement of the magnitude of side-etching is important to control the structural dimensions in etching. FIG. 13 shows an example of a section near the VLSI surface after etching. In this figure, the etched layer 202 on the substrate 204 and insulating layer 203 is etched according to the resist 201.
In FIG. 13, x indicates the side-etching magnitude. Ideally it is desirable that x is zero, however, even if the sample stand is inclined, the side-etching area is in the shadow and cannot be observed. Therefore, the stereo method cannot be employed. For this reason, in the prior art, when measuring the magnitude of a side-etching, the VLSI was cut and the section was observed with SEM. However, the VLSI was destroyed and the preparation of the cut samples required much time.